Polymeric micelles for parenteral delivery of sagopilone: physicochemical characterization, novel formulation approaches and their toxicity assessment in vitro as well as in vivo.

PURPOSE: The block copolymers PEG(2000)-b-PLA(2200), PEG(2000)-b-PCL(2600) and PEG(5000)-b-PCL(5000) have been currently identified as optimal solubilizing agents for Sagopilone, a poorly water-soluble anticancer drug. In the present study, the stability, formulation feasibility and in vitro as well as in vivo toxicity were evaluated. METHODS: Dispersion media, storage conditions, and dilutions were varied for stability assessment. The critical micelle concentration (CMC) was determined using a fluorescent probe technique. Lyophilizates and polymeric films were investigated as formulation options. Furthermore, the toxicity was studied in vitro and in vivo using HeLa/MaTu cells and a nude mouse model, respectively. RESULTS: A drug-polymer ratio as low as 1:20 (w/w) was sufficient to solubilize Sagopilone effectively and to obtain stable dispersions (24h: drug content >or= 95%). Although the micelles exhibited a similar thermodynamic stability (CMC: 10(-7)-10(-6)M), PEG-b-PCL micelles were kinetically more stable than PEG(2000)-b-PLA(2200) (24h at 37 degrees C: drug content >or= 90% compared to 30%, respectively). Lyophilization of PEG-b-PCL micelles and storage stability of solid drug-loaded PEG(2000)-b-PLA(2200) films (3m, 6 degrees C: drug content of (95.6+/-1.4)%) were demonstrated for the first time. The high antiproliferative activity has been maintained in vitro (IC(50)<1 nM). Carrier-associated side effects have not been observed in vivo and the maximum tolerated dose of micellar Sagopilone was determined to be 6 mg/kg. CONCLUSION: The results of this study indicate that polymeric micelles, especially PEG-b-PCL micelles, offer excellent potential for further preclinical and clinical cancer studies using Sagopilone.

Cost effectiveness of ixabepilone plus capecitabine for metastatic breast cancer progressing after anthracycline and taxane treatment.

PURPOSE: Using data from a recent randomized trial, we evaluated the cost effectiveness of ixabepilone plus capecitabine versus capecitabine alone in patients with predominantly metastatic breast cancer considered to be taxane-resistant and previously treated with or resistant to an anthracycline. METHODS: We developed a stochastic decision-analytic model to represent data collected in the trial on medical resource use, health-related quality of life, and clinical outcomes. Estimates of overall survival were conditional on level of tumor response. We assigned monthly costs and utility weights according to periods defined by the duration of study treatment, time from discontinuation of the study drug until disease progression, and from progression until death and were specific to the level of response and receipt of subsequent therapy. Medical resources were valued in 2008 US dollars. We performed Monte Carlo simulations and sensitivity analyses to evaluate model uncertainty. RESULTS: Overall survival was significantly associated with level of tumor response (P < .001). Total costs were estimated at $60,900 for patients receiving ixabepilone plus capecitabine and $30,000 for patients receiving capecitabine alone. The estimated gain in life expectancy with ixabepilone was 1.96 months (95% CI, 1.36 to 2.64 months); the estimated gain in quality-adjusted survival was 1.06 months (95% CI, 0.09 to 2.03 months). The resulting incremental cost-effectiveness ratio was $359,000 per quality-adjusted life-year (95% CI, $183,000 to $4,030,000). In sensitivity analyses, the results were robust to changes in numerous inputs and assumptions. CONCLUSION: Addition of ixabepilone to capecitabine adds approximately $31,000 to overall medical costs and affords approximately 1 additional month of quality-adjusted survival.